The cystatin superfamily encompasses proteins that contain multiple cystatin-like sequences. Some of the members are active cysteine protease inhibitors, while others have lost or perhaps never acquired this inhibitory activity. There are three inhibitory families in the superfamily, including the type 1 cystatins (stefins), type 2 cystatins and kininogens. This gene encodes a stefin that functions as an intracellular thiol protease inhibitor. The protein is able to form a dimer stabilized by noncovalent forces, inhibiting papain and cathepsins l, h and b. The protein is thought to play a role in protecting against the proteases leaking from lysosomes. Evidence indicates that mutations in this gene are responsible for the primary defects in patients with progressive myoclonic epilepsy (EPM1). One type of mutation responsible for EPM1 is the expansion in the promoter region of this gene of a CCCCGCCCCGCG repeat from 2-3 copies to 30-78 copies. [provided by RefSeq, Jul 2016]

Gene RIF (43)

Even though the majority of EPM1 patients have a uniform genetic mutation, the actual size of the longer CSTB expansion mutation allele is likely to have a modulating effect on the age at disease onset, myoclonus severity, and cortical neurophysiology.

Data shows that CYTB and ANXA4 overexpression may be involved in carcinogenesis and histopathological differentiation of ovarian clear cell carcinoma and suggest they may serve as a potential diagnostic biomarkers.